Kaolin-derived Cu(ii)-doped zeolite supported on nickel foam for electrochemical paracetamol detection

A kaolin-derived Cu(ii)-doped zeolite (Cu-Z₁) was synthesized through metakaolin activation, alkaline crystallization, and subsequent Cu²⁺ ion exchange, and immobilized on nickel foam (Cu-Z₁/NiF) for electrochemical determination of paracetamol. The synthesized materials were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS), X-ray photoelectron spectroscopy (XPS), and thermogravimetric/differential thermogravimetric analysis (TGA/DTGA). The characterization results confirmed preservation of a ZSM-5-type aluminosilicate framework following Cu(ii) incorporation, with accompanying changes in crystallinity, morphology, and surface chemical environment. Electrochemical measurements demonstrated enhanced paracetamol oxidation at Cu-Z₁/NiF compared with bare nickel foam and undoped Z₁/NiF, giving an anodic peak current of 75.69 µA, a midpoint potential of 355 mV, and reduced charge-transfer resistance. Under optimized conditions, differential pulse voltammetry (DPV) showed a linear response over 5-100 µM paracetamol, with a detection limit of 0.3926 µM, sensitivity of 2.0456 µA µM^-1 cm^-2, and R ² = 0.9971. The sensor exhibited good selectivity toward paracetamol in the presence of dopamine, uric acid, and glucose, with repeatability below 0.8% RSD. It retained 95.8% of its initial response after 20 days. Analysis of commercial paracetamol tablets produced recoveries of 95.91-99.29%, demonstrating the applicability of the Cu-Z₁/NiF sensor for pharmaceutical paracetamol determination.